Tooth decay, also known as dental caries, is one of the most common human diseases, after the common cold, and affects all age groups. Dental caries is caused by acid erosion of tooth enamel, typically resulting in a carious lesion or cavity in the tooth enamel, or underlying dentin or pulp. A dental filling, also called a dental restoration, is an emplacement of non-native material in a tooth, and is a process used to retain the functionality, integrity and morphology of tooth structure. The dental restoration process typically involves removing the carious and/or infected tooth material, usually using a handheld dental handpiece (a high speed handheld drill), filling the resulting cavity in the tooth with one or more dental restoration materials, and forming the restoration material to the desired shape in the tooth before it solidifies to form the completed restoration. Dentists are trained to be experts at interpretation of their tactile and visual senses as one of their only tools to manage and manipulate the tools (such as the dental handpiece or drill) used to perform the tooth restorations as well as other daily dental operations, many of which may require the precise removal of undesired carious or otherwise diseased tooth material, while leaving adjacent healthy or desired tooth material undamaged and intact. The high rotational speed of modern powered dental handpiece tools, small available space in the patient's mouth for maneuvering such tools particularly to reach remotely located caries in the mouth, and the necessity of working on conscious patients are key factors that affect the accuracy and reliability of a dentist's use of their tactile and visual senses to control the removal of tooth material during a procedure. If the additional factors of dentist's periodic fatigue and humans' typically slow responses to sudden changes, are also considered in light of the fact that powered dental handpieces can easily remove a large portion of a tooth with a small motion of the wrist or fingers (or due to movement by the patient), then the problem of accurately controlling the process of removing tooth material with a powered dental handpiece typically becomes even more serious. It can therefore be concluded that with current restoration and treatment routines, the undesired loss of dental structure due to inadvertent over-removal of healthy tooth material may be common and inevitable. It should be emphasized that tooth structure is one of the few parts that the body that is not biologically reproduced or healing, and that therefore any undesired loss of tooth structure will be permanent. Similar to removing dental caries, the replacement of restorations may result in the loss of healthy dental structure.
X-ray and clinical tactile and visual bases identification techniques are the principal tools used by dentists to detect cavities or other diseased tooth areas; however, such diagnostic tools typically do not reveal complete information regarding the depth and/or size of caries or other lesions, particularly at depth within a tooth. Therefore, such current diagnostic and control methodologies may typically be insufficient to provide a dentist with the ability to optimally and selectively remove tooth material throughout common dental restoration procedures. Further, dental restorations are not just limited to cavity removal and filling processes. Although dental fillings may not degrade particularly quickly, external forces imposed on restorations such as by clenching or grinding of teeth causes fatigue of the restoration structure, leading to development of cracks and ultimately failure. The performance of dental restorations may typically be subject to several factors, including the performance and characteristics of restorative materials used, the dental practitioner's level of experience, the type and position of tooth, the restoration's shape, size and number of restored surfaces, and the patient's age and health. If an old filling or other restoration collapses, there is a high potential for developing new decay that requires removal and replacement of the old restoration and removing any related further decay or cavities. Replacing of old restorations is still one of the most frequently performed procedures in clinical dental practice and which typically exceeds in number the removal and restoration of new carious lesions. The high rate of required removal and replacement of old restorations does not appear to have declined in spite of all modern advancements in the field of dental restoration materials. Replacing a dental restoration, however, does not exclude the likelihood of the same imperfections occurrence, nor the prevention of new lesions and/or secondary caries from eventually occurring in the newly replaced restoration. Similar to the original removal of dental caries, the replacement of previous restorations may frequently also result in undesired loss of healthy dental structure due to poor identification and selective removal of restoration and/or diseased tooth material particularly through use of powered dental handpiece tools.
The most commonly used dental restorative materials are amalgam and composites. Dental amalgam is low cost, easy to handle and inhibits the growth and reproduction of bacteria. The rate of amalgam fillings has recently declined due to adverse health concerns. This has created a shift in restorative dentistry toward use of composite materials. Although high quality composite restoration materials and better restoration techniques have improved their longevity, restoration replacement rates have continued to become significantly higher and the evolution of caries in composite restorations is typically faster than in amalgam based restorations. This appears to indicate that more restoration replacements and even more resultant undesired tooth structure loss due to the perfect color matching of composite restorations to the surrounding original tooth, which may further complicate the ability of dentists to accurately identify and selectively remove restoration material separate from desired tooth structure material.
In addition to procedures related to caries removal and dental restorations, a further dental procedure for which additional assistance is desirable for dental practitioners is in relation to installation of dental implants. In a dental implant procedure a dental practitioner typically makes a small hole inside the patient's jaw and in several steps then enlarges the opening sufficiently to prepare it for insertion of a dental implant. During the dental implant installation procedure dental practitioners typically cannot see inside the hole in the patient's jaw, and instead typically rely solely on their tactile senses. Such “blind” operation presents a real danger that if the dental handpiece enlarges the implant cavity too much or extends it too deeply, nerve damage may occur with potentially permanent and serious consequences for the patient.
Accordingly, there remains a need for techniques and apparatus to improve the ability to selectively identify and remove desired dental materials such as decayed or diseased tooth (caries and/or cavities) material, restoration material and healthy original tooth material from one another, and to improve control of powered dental handpiece tools in performing such removal.